GB1564772A

GB1564772A - Multi-container package

Info

Publication number: GB1564772A
Application number: GB23373/77A
Authority: GB
Original assignee: Owens Illinois Inc
Current assignee: OI Glass Inc
Priority date: 1976-06-09
Filing date: 1977-06-02
Publication date: 1980-04-16
Also published as: AU510323B2; AU2587677A; CA1113047A; DE2723762C2; FR2354258B1; DE2723762A1; JPS5754384B2; FR2354258A1; MX146199A; JPS52152395A

Description

(54) A MULTI-CONTAINER PACKAGE (71) We, OWENS-ILLINOIS, INC. a corporation organized and existing under the laws of the State of Ohio, United States of America, of Toledo, State of Ohio, United States of America, (assignee of JAMES ELMER HEIDER), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a package of two or more containers such as cans, bottles, jars, cannisters, made of glass, metal, or rigid plastic or paper. In a more specific aspect the present invention relates to an improved merchandising package for a plurality of such a containers wherein performance, economy, and appearance of the package are primary considerations.

Today's marketing of bottled and canned beverages and other products calls for suitably packaged clusters of such containers, perhaps the most familiar of which is the socalled "six-pack". The package must safely and firmly hold the containers, it must lend itself both to ready indendent portability for consumer use and to bulk stacking for warehousing and shipment, and it must lend itself to reliable and economical massproduction. The advent of shrinkable plastic overwraps has resulted in drastic changes from the cardboard packages of the past and U.S. Patents 3,532,214; 3,198,327; 3,552,559; 3,834,525; Re 28,535; 3,650,394; 3,650,395; 3,817,373; 3,416,288; 3,747,749: 3,331,503; 3,302,784: 3,477,564; 3,756,397; and 3,217,874 are representative of packages with plastic overwrap.Most of these patents are concerned with the use of various transparent, nonfoam shrink wrap packages and to the use of various handles, "fingerholes" and adjunct supporting structures.

Multicontainer packages using this transparent thermoplastic films are suitable for many applications although there are marked disadvantages for the packaging of glass containers containing products such as beer which are sensitive to light. Furthermore such thermoplastic films do not provide a great deal of cushioning protection in handling. It is also quite difficult to decorate such transparent thermoplastic films and such packages often require the attachment of supplemental labels for the purpose of identification and decoration.

It is noted that U.S. Patent 3,400,810 discloses the use of foam polystyrene for shrink wrapping of multicontainer packages. However, the foam polystyrene disclosed in this patent is biaxially oriented and will shrink in both directions. Such a shrunken overwrap will have the same strength properties in both directions making removal of the containers somewhat difficult. Furthermore it will be difficult to form a seal on the end flaps of package cluster due to axial as well as circumferential shrinkage of the overwrap. It is noted that the packages illustrated in this patent engage only a small fraction of the end containers in the cluster. Moreover it is necessary for the patentee to use a very thick film in the neighbourhood of 40 mils to achieve the required strength.

Thus it is the primary object of the present invention to provide an improved multicontainer merchandising package which is strong but yet is easily opened, opaque to light and is capable of being preprinted with information or decoration prior to application and requires no external structure for handling purposes.

The present invention provides a multiple container package comprising a group of similarly shaped containers held together in side-by-side fashion by a plastic overwrap; the overwarp being in the form of an open-ended opaque sleeve disposed around the containers with the axial direction of the sleeve lying normal to the axial direction of the containers and shunk around the containers to leave apertures at opposite ends of the package of smaller area than the area of the corresponding package end; the sleeve being formed of a shrinkable thermoplastics material which is uniaxially oriented in the circumferential direction and comprises a closed cellular thermoplastic polyolefin layer laminated to a noncellular thermoplastic polyolefin film, the polymeric material in said layer and film being a homopolymer, or a copolymer or a polymer blend comprising at least 60% by weight olefin moieties.

In one embodiment of the present invention the heat shrinkable polymeric sleeve is of a composite structure having a layer of a closed cellular (e.g. foam) olefin polymer adhered to a layer of a noncellular olefin polymer film wherein the cellular layer is in on the inside of the sleeve so as to engage with at least the tops of containers and the film is on the outside of the sleeve and has a smooth, glossy decorated surface.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective illustration of a "six-pack" of glass bottles, in accordance with the present invention; Fig. 2 is a bottom view of the package of Fig. 1; Fig. 3 is a perspective illustration of a six-pack of cans, in accordance with the present invention; Fig. 4 is a perspective illustration of a 12-pack of glass beer bottles, in accordance with the present invention; and Fig. 5 is a cross sectional illustration of the composite laminate used as the overwrap in Figs. 1 through 4.

Referring now to Figs. 1 and 2 reference numeral 10 generally refers to the cluster package of six conventional upstanding one-way beer bottles 15 having similar cylindrical bodies. The containers are arranged in two adjacent rows each having three side-by-side containers.

As can be seen in Fig. 1 the tops 12 of the bottles 15 are snugly engaged by sleeve 11 and the bottles are contained and confined in all directions so as to prevent relative movement of the individual containers within the package. Fig. 2 illustrates how the bottoms 16 of bottles 15 are also snugly engaged by the sleeve. The heat shrunk opaque, overwrap sleeve of invention is indicated by reference numeral 11 and is applied so that the direction of uniaxial orientation is in the circumferential or radial direction of the sleeve. Sleeve 11 is shown with decoration of a general "X" form.

Such decoration is applied prior to wrapping the sleeve around the package.

The sealing seam of the sleeve is designated by lia and is shown as being positioned on the lower side of the package.

The seam is formed by the use of adhesives or by thermally fusing edges of the sleeve together. The seam is positioned on the side of the package as a matter of convenience and could also be located at the bottom or top of the package.

The open end of the sleeve 11 defines an aperture 13 which is formed as the overlaying ends of the sleeve shrink and fuse together; the aperture being of smaller area than the respective end of the package. The other end of the package (not shown) has similar configuration and appearance. In forming aperture 13 there is some shrinkage in the sleeve (e.g. less than 10%) in the axial direction and this assists in the formation of the tight package. If there were too much shrinkage in the axial direction, the aperture would be too large, and the sleeve would not effectively retain the bottles. In this regard it is important that the sleeve extend to cover the point of farthest extension of the container from the package so as to prevent container-to-container impact when several of such packages are transferred in end-to-end fashion on a conveyor.This point is approximately designated by the lead line for reference numeral 13 in Fig. 2.

The upper rim 13a of aperture 13 is quite functional and serves as a convenient gripping surface for transporting the package.

Due to the nature of the uniaxially orientation, rim 13a is quite strong against the stress of lifting at this point and readily supports the weight of containers and their contents.

To open the package all one need do is punch a hole with the finger or other instrument through the top of the package at point between tops 12 where the sleeve is tightly drawn. Such a point is generally illustrated by reference numeral 14. Once the sleeve is punctured in these areas it will readily tear in the circumferential direction and the bottles can be easily removed individually or in pairs. The sleeve is quite resisting to tearing in the axial direction so the package remains intact with respect to the remaining containers in the cluster.

Fig. 3 generally illustrates a package 20 similar to that shown in Figs. 1 and 2, ex cept that the containers are in the form of cylindrical metal cans 21 rather than bottles. The sleeve 23 is otherwise as explained with respect to Figs. 1 and 2 and is sealed together at seam 22.

Fig. 3 also illustrates how finger opening can be used with the package of inven tion if desired although the finger hole is not used in the presently preferred embodiment. Reference numeral 25 represents a finger slit which is cut in the circumferential direction on sleeve 23. The slit terminates in semicircular cuts 25a which serve to retard tearing in the circumferela tial direction upon carrying. It will be understood that some care must be exercised when carrying the package by finger slits.

Reference numeral 24 represents another type of circumferential finger slit which is formed by pushing a hot loop of wire through the sleeve. Slit 24 is sealed by beaded edges 24a which are formed by contact with the hot wire. In practice it is likely that all the slits on one package will be of the same type.

Fig. 4 generally illustrates a 12-pack 30 of one-way beer bottles arranged in three rows of four bottles each confined by sleeve 30 in tray 32. The package configuration is generally the same for that shown in Figs. 1 and 2 except that the bottoms of containers 31 set in tray 32 which is shown as being made of corrugated fiber board.

The outline of tray 32 is generally seen under the sleeve 30 and comprises a flat bottom panel provided with short upstanding side walls on all sides. Tray 32 is used for added package rigidity when more than two rows of containers are packaged to prevent relative displacement of the packaged containers with respect to each other. Due to the use of tray 32 only the tops 34 of the bottles are snugly engaged by sleeve 30 and the bottoms of the containers are held securely against the tray.

Sleeve 30 is applied so that the direction of uniaxially orientation is in the circumferential or radial direction of the sleeve and two sealing seams 33 are shown as being positioned on the lower part of the package overlaying the side wall portion of the tray 32. In this embodiment the sleeve is applied and sealed as two separate sheets.

That part of the sleeve covering the bottom of the tray need not be foamed and can be any compatible thermoplastic film.

In some embodiments it may be preferred to use a less expensive non-decorated thermoplastic film for covering the bottom of the tray. Furthermore transparent films can be used to cover the tray bottoms when it is desired or required to read specifications or other information printed on the tray bottom. As a further embodiment the sleeve can be formed by sealing the composite to the tray at the point where sealing seams 33 are located. In this embodiment the bottom of the tray serves as a part of the sleeve. It is thus apparent that the entire sleeve need not be made of the composite so long as the composite circumscribes the containers and snugly engages the tops of the containers in shrink fit relation. In this regard the term sleeve as used herein refers to this relationship.

As has been previously described with respect to Fig. 1 the rim 35 of the aperture 36 in the end of sleeve 30 provides a convenient handle for carrying. Most 12-packs would probably be too heavy to permit the use of finger holes. The end of the package which is not shown is identical in configuration to the end shown.

Fig. 5 shows a cross sectional view of the sleeve of Figs. 1 through 4 with 40 representing the foam or cellular layer and 41 representing the noncellular film laminated thereto. The total thickness of the laminate composite is usually in the range of about 3 mils to about 20 mils and preferably in the range of about 5 to about 15 mils for efficiency and economy. The cellular layer 40 is usually about 2 to about 5 times and preferably about 3 times the thickness of noncellular film 41 and noncellular layer 41 is usually positioned on the outside of the sleeve.

The polymeric materials respectively and independently contemplated for cellular layer 40 and noncellular layer 41 are olefin polymers; that is, each of these polymeric layers will have as the predominant polymeric moiety a polymer of an olefin, preferably an olefin having 2-4 carbons, or mixtures thereof, e.g. the predominant moiety will be a polymer of ethene, propene, bulene, like butene-l, or mixtures thereof, more commonly referred to as a polymer of ethylene, propylene or butylene.This includes homopolymers, copolymers of these olefins with other copolymerizable monoethylenically unsaturated monomers, wherein the olefin in the copolymerization is such that the moiety thereof in the final copolymer, that is the ethylene, propylene or butylene moiety, is at least about 60% by weight, and polymeric blends, or admixtures, wherein the resulting polymeric blend is at least about 60% by weight of a polymerized olefin moiety, e.g. at least about 600", of an ethylene moiety in the blend.

The minor amounts, i.e. less than about 405/, of the other moiety of material employed, are such as to supplement and compliment the basic properties of the olefin polymer and this applies whether other moieties are introduced by way of a polymer blend, or admixture, or by way of a copolymerized monomer. These other moieties, whether supplied by blending another polymer with a homopolymerized olefin, e.g. homopolymerized ethene, (ethylene homopolymer), or by copolymerization therewith, should not be such as to significantly interfere with the foamable, heat sealable, heat shrinkable, extrudable characteristics of the base olefin polymer and should be compatible, i.e. miscible with it.

Exemplary olefin homopolymers are ethylene, propylene and butylene homopolymers, with the former being especially preferred, and blends of these homopolymers. The terms polyethylene, polypropylene and polybutylene are used herein to include those materials recognized and sold commercially under those names, even though those materials, strictly and technically, may be viewed by some to be a blend, or copolymer, since the materials may include small amounts typically less than about 5%, e.g. 0.5-3% by weight, of another polymeric moiety. For example, polyethylene is sold and recognized by that name when in fact it may be produced by copolymerization with 1-2 percent by weight of hexene, or butadiene, or may, by analysis show several percent, e.g. 3-5% of vinyl acetate moiety; for practical purposes however these materials consist of polyethylene.

In this regard the composition of the sleeve used in the present invention is the same composition as the laminate described in British Patent Specification No. 1,526,944 relating to a container provided with a heat shrunk cellular sleeve.

The foregoing generally describes the composition of the polymeric portion of the cellular layer 40 and noncellular film 41, it being understood that the layers need not be of the same polymeric composition.

It will, of course, be apparent that suitable adjuvants can be present in these layers if desired. Thus, for example in addition to the polymeric material, the respective layers can include pigments, stabilizers and the like. Generally, excellent results will be obtained by selecting a polymeric composition for cellular layer 40 which has a melt index or melt flow of less than 5, for example between about 0.1 to 5 and most desirably about .2 to 1 and the polymeric material selected for the noncelluar layer 41 will have a melt index or melt flow of less than about 10.The preferred material for both the cellular layer and the noncellular layer is polyethylene, which includes low density polyethylene, for example polyethylene having a density of less than 0.925 grams/cc, generally in the range of about 0.910 to about 0.925, high density polyethylene, for example that having a density greater than about 0.941, typically about 0.941 to about 0.965, medium density polyethylene, and blends thereof. As regards the cellular layer, the density specified is prior to foaming.The foamed density of cellular layer is about 25-30 Ib/ft.3 and the density of the composite laminate is about 3540 Ib/ft.3 As previously indicated the present invention is directed to an improvement in the hereinbefore-described packages wherein, in producing these packages, a heat shrinkable uniaxially oriented, laminated sheet is first prepared which is appropriately cut and slit and formed into rectilinear sheets which are then formed into a heat shrinkable sleeve which applied to the cluster of containers to produce the ultimate package.

While a sheet of stock material of the composite structure for use herein can be formed by various techniques it is generally preferred to employ extrusion technology.

This extrusion technology may take either of two conventional forms, one of which is extrusion coating and the other of which is the use of co-extrusion technology. The latter technique, however, is particularly highly preferred because of the apparent ability to form lower density composite structures. In the co-extrusion technique, while a slit die may be employed, the preferred practice is to employ an extrusion die which is possessed of an annular, circular opening and the composite structure is initially formed as a tubular shape by what is referred to in the art as a "blown bubble" technique. These types of co-extrusion dies are widely available commercially and an exemplary die is set forth in SPE Journal, November 1969, Vol. 25, page 20, entitled, "Co-Extrusion of Blown Film Laminates" and form no part of the present invention as such.

In this known co-extrusion technique the circular opening is fed from two independent extruders and, in this particular instance, the extruder supplying the foamable material, intended to form cellular layer 40, preferably will feed the die so that this material forms the internal portion of the tubular extrusion; the extruder feeding the material intended to form non-cellular layer 41 will preferably be fed to the die so as to form the external portion of the tubular shape. The tubular member issuing from the extruder is blown into a bubble by conventional "bubble" forming techniques, including air cooling of the external surface thereof, and is then drawn through the nip of two juxtaposed rollers wherein the tubular member is compressed to form a flattened tube.

Suitable convention foaming or blowing agents are employed to produce foaming and the cellular structure results, just as the extrudate leaves the die. This flattened tube is then contacted with cutting knives which slit the flattened tubular member along its edges (machine direction) so as to form a sheet or film of substantially uniform width; this sheet or film, which is at this point actually a sheet of two superimposed composite structures, for use herein, is separated into two independent sheets and wound onto independent winding wheels, which provides the stock of the heat shrink able composite structure for use herein.Inasmuch as the sheet of the composite structure must possess heat shrinkable characteristics the appropriate heat shrinking in the machine direction of extrusion, which preferably is a major amount and is greater than the cross direction heat shrinkage, is primarily provided by the impetus of the rate of drawing of the flattened tube through the nip of the rolls, and using cooling air on the exterior of the bubble, and the cross direction shrinkage, which is less than the machine direction shrinkage, is primarily provided by the internal air employed in forming the bubble and external cooling air. This of course is known for forming heat shrinkable films.

The term "heat shrinkable" as used herein refers to the property of the laminated composite whereby it contracts upon exposure to sufficient heat. Shrinking is gene rally attributable to a reorientation of molecules which were previously oriented by stretching the sheet either uniaxially longitudinally (machine direction) or hori zontally (transverse direction) or biaxially (both directions). In the present invention the laminated composite sleeve used is uniaxially oriented in the circumferential direc tion, that is, it is capable of shrinkage in that direction more than it is in the axial direction. Preferably, the sleeve is capable of shrinkage in circumferential direction of at least about 2.5 times and preferably at least about 5 times the shrinkage in the axial direction.The sleeves of invention are capable of shrinking at least 50% and preferably at least 60% in the circumferential direction and less than 20% and preferably less than 10% in the axial direction. In a particular preferred embodiment the sleeve is capable of shrinkage about 70% in the circumferential direction at about 6-8% in the axial direction. This shrinkage value is theoretical value rather than value which is experienced in forming a package. The theoretical values are determined by placing a sample of the composite in a hot bath of heat transfer liquid at 350"F for 10 seconds and determining the resulting shrinkage. In actual practice the shrinkage is usually much less than theoretical due to the amount of the composite that is used to wrap the containers.For example a sheet of composite foam polyethylene and film polyethylene with a foam thickness of about 4.5 mils and a film thickness of about 1.5 mils, which is 21.5 inches long and about 11.5 inches wide forms the sleeve around a six-pack of one-way beer bottles when heated at 400 F for 20 seconds.

In such a package there is an actual shrinkage of about 50% in forming the aperture at the end of the pack, about 15% between bottles and only about 2% over the bottle tops.

The term "heat shrunk" describes the condition of a heat shrinkable material after application thereto of heat sufficient to cause relaxation and shrinkage (e.g. heating in an oven at 450"F for about 5 seconds).

This heat treatment heats the sleeve to near the melting point of the composite.

The sleeve can be applied by conventional method wherein a plurality of containers are carried along a predetermined path which can be a pair of moving conveyors or other transport means to an arranging zone such as an indexer where the containers are arranged in the desired juxtaposed relation. Typically this relation is three rows of containers two abreast. The arranged containers are moved along a path away from the arranging station to a wrapping station where heat shrinkable composite laminate from a supply roll is placed around the arranged containers. The wrap is parallel to the longitudinal axis of the arranged container cluster or provided the ends of the outermost containers are within the volume defined by the sleeve after shrinkage.

The wrapped containers are then passed through a heating zone such as a shrink tunnel where heat sufficient to shrink the film is applied. The arranged containers held endwise and sidewise by the heat shunk sleeve are then passed to a distribution area.

WHAT WE CLAIM IS: 1. A multiple container package comprising a group of similarly shaped containers held together in side-by-side fashion by a plastic overwrap; the overwrap being in the form of an open-ended opaque sleeve disposed around the containers with the axial direction of the sleeve lying normal to the axial direction of the containers and shrunk around the containers to leave apertures at opposite ends of the package of smaller area than the area of the corresponding package end; the sleeve being formed of a shrinkable thermoplastics material which is uniaxially oriented in the circumferential direction and comprises a closed cellular thermoplastic polyolefin layer laminated to a noncellular thermoplastic polyolefin film, the polymeric material in said layer and film being a homopolymer, or a copolymer or a polymer blend comprising at least 60% by weight olefin moieties.

2. A package as claimed in claim 1 wherein said polyolefin layer is polyethylene.

3. A package as claimed in claim 1 or 2 wherein said polyolefin film is polyethylene.

4. A package as claimed in claim 1, 2 or 3 wherein the sleeve has a thickness of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. able composite structure for use herein. Inasmuch as the sheet of the composite structure must possess heat shrinkable characteristics the appropriate heat shrinking in the machine direction of extrusion, which preferably is a major amount and is greater than the cross direction heat shrinkage, is primarily provided by the impetus of the rate of drawing of the flattened tube through the nip of the rolls, and using cooling air on the exterior of the bubble, and the cross direction shrinkage, which is less than the machine direction shrinkage, is primarily provided by the internal air employed in forming the bubble and external cooling air. This of course is known for forming heat shrinkable films. The term "heat shrinkable" as used herein refers to the property of the laminated composite whereby it contracts upon exposure to sufficient heat. Shrinking is gene rally attributable to a reorientation of molecules which were previously oriented by stretching the sheet either uniaxially longitudinally (machine direction) or hori zontally (transverse direction) or biaxially (both directions). In the present invention the laminated composite sleeve used is uniaxially oriented in the circumferential direc tion, that is, it is capable of shrinkage in that direction more than it is in the axial direction. Preferably, the sleeve is capable of shrinkage in circumferential direction of at least about 2.5 times and preferably at least about 5 times the shrinkage in the axial direction.The sleeves of invention are capable of shrinking at least 50% and preferably at least 60% in the circumferential direction and less than 20% and preferably less than 10% in the axial direction. In a particular preferred embodiment the sleeve is capable of shrinkage about 70% in the circumferential direction at about 6-8% in the axial direction. This shrinkage value is theoretical value rather than value which is experienced in forming a package. The theoretical values are determined by placing a sample of the composite in a hot bath of heat transfer liquid at 350"F for 10 seconds and determining the resulting shrinkage. In actual practice the shrinkage is usually much less than theoretical due to the amount of the composite that is used to wrap the containers.For example a sheet of composite foam polyethylene and film polyethylene with a foam thickness of about 4.5 mils and a film thickness of about 1.5 mils, which is 21.5 inches long and about 11.5 inches wide forms the sleeve around a six-pack of one-way beer bottles when heated at 400 F for 20 seconds. In such a package there is an actual shrinkage of about 50% in forming the aperture at the end of the pack, about 15% between bottles and only about 2% over the bottle tops. The term "heat shrunk" describes the condition of a heat shrinkable material after application thereto of heat sufficient to cause relaxation and shrinkage (e.g. heating in an oven at 450"F for about 5 seconds). This heat treatment heats the sleeve to near the melting point of the composite. The sleeve can be applied by conventional method wherein a plurality of containers are carried along a predetermined path which can be a pair of moving conveyors or other transport means to an arranging zone such as an indexer where the containers are arranged in the desired juxtaposed relation. Typically this relation is three rows of containers two abreast. The arranged containers are moved along a path away from the arranging station to a wrapping station where heat shrinkable composite laminate from a supply roll is placed around the arranged containers. The wrap is parallel to the longitudinal axis of the arranged container cluster or provided the ends of the outermost containers are within the volume defined by the sleeve after shrinkage. The wrapped containers are then passed through a heating zone such as a shrink tunnel where heat sufficient to shrink the film is applied. The arranged containers held endwise and sidewise by the heat shunk sleeve are then passed to a distribution area. WHAT WE CLAIM IS:

1. A multiple container package comprising a group of similarly shaped containers held together in side-by-side fashion by a plastic overwrap; the overwrap being in the form of an open-ended opaque sleeve disposed around the containers with the axial direction of the sleeve lying normal to the axial direction of the containers and shrunk around the containers to leave apertures at opposite ends of the package of smaller area than the area of the corresponding package end; the sleeve being formed of a shrinkable thermoplastics material which is uniaxially oriented in the circumferential direction and comprises a closed cellular thermoplastic polyolefin layer laminated to a noncellular thermoplastic polyolefin film, the polymeric material in said layer and film being a homopolymer, or a copolymer or a polymer blend comprising at least 60% by weight olefin moieties.

in the range of about 3 mils to about 20 mils.

5. A package as claimed in claim 4 wherein said sleeve has a thickness of about 5 to about 15 mils.

d. A package as claimed in any of claims 1 to 5 wherein the thickness of said closed cellular layer is about 2 to about 5 times the thickness of said film.

7. A package as claimed in claim 6 wherein the thickness of said closed cellular layer is about 3 times the thickness of said film.

8. A package as claimed in any of claims 1 to 7 wherein said film is on the outside of said sleeve.

9. A package as claimed in any of claims 1 to 8 wherein said sleeve is decorated.

10. A package as claimed in any one of claims 1 to 9 wherein the thermoplastic material is capable of shrinking in the circumferential direction at least 2+ times the amount of shrinkage in the axial direction.

11. A package as claimed in claim 10 wherein the thermoplastics material is capable of shrinkage in the circumferential direction at least about 5 times the amount of shrinkage in the axial direction.

12. A package as claimed in any one of claims 1 to 11 wherein said sleeve has finger openings.

13. A package substantially as hereinbefore described with reference to the ac companying drawings.